Elderly cancer patients may differ from younger patients in their preferences for treatment, in decisional style, and in the kinds of information. In addition, both the prevalence of cognitive disorders and risk for delirium in severe illness increase among the elderly. This discussion presents research findings on decisional style in the elderly and on determination of decisional capacity. The legal standard of capacity requires demonstrating understanding, appreciation, reasoning and stating a choice. We present formal screening tools and informal interview techniques for assessment, as well as guidelines for when formal assessment may be helpful.